The present invention concerns the preparation of a new series of ester derivatives of hyaluronic acid, biocompatible threads in a multifilament conformation comprising filaments constituted by such derivatives, and their use in the fields of medicine and surgery.
Suture threads are now widely used in modern surgical practice and can be made of a wide range of materials, according to the type of surgery to be performed (Abraham R. Katz et al. xe2x80x9cA new synthetic monofilament absorbable suture made from polytrimethylene carbonatexe2x80x9d Surgery, Gynecology and Obstetrics, September 1985, vol. 161, pages 213-222; Abraham R. Katz et al. xe2x80x9cEvaluation of tensile and absorption properties of polyglycolic acid suturesxe2x80x9d Surgery, Gynaecology and Obstetrics, October 1970, vol. 131, pages 701-716). It is possible, therefore, to imagine different types of suture thread with different characteristics of gauge, tensile strength, biocompatibility and biodegradability, according to whether they are intended for extensive lacerations (abdominal wall, thorax, lower limbs), or for small cuts and wounds as on the face, mouth and soft tissues. Some conditions require the material to be biocompatible but not biodegradable (as in cardiovascular surgery), while others necessitate both these characteristics (as in surgery to the urinary tract). The suture threads currently on the market vary first and foremost in the type of polymer with which they are made. Indeed, they vary from non-reabsorbable threads based on polyester, polypropylene, nylon and silk, such as Surgilene(copyright), Surgilon(copyright), Novafil(copyright) and Dermalon(copyright) by DG (Davis+Geckxe2x80x94American Cyanamid Company), to reabsorbable threads based on glycolic acid and collagen, such as Vicryl(copyright) and Catgut(copyright) by Ethicon (A. Pavan et al. xe2x80x9cA Comparative Study of Poly(Glycolic acid) and Catgut as Suture Materials. Histomorphology and Mechanical Propertiesxe2x80x9d, Journal of Biomedical Materials Research, vol. 13, pages 477-496, 1979). As these materials all have a synthetic polymeric matrix, they are poorly biocompatible and only some of them are biodegradable, so they may cause inflammatory reactions at the lesion site where they are applied (E. A. Bakkum et al. xe2x80x9cQuantitative analysis of the inflammatory reaction surrounding sutures commonly used in operative procedures and the relation to postsurgical adhesion formationxe2x80x9d Biomaterials 1995, vol. 16, No. 17, pages 1283-1289) and may necessitate a second surgical operation to remove them from the application site. In particular the materials used to date to stitch wounds have given rise to an inflammatory response and hyperfibrotic process, because the organism recognises that they are foreign bodies. On account of this phenomenon, hypertrophic scars and keloids are prone to form around the stitches any of the anatomical or functional characteristics of healthy tissues. Apart from being unsightly, such scars may. If they are external, cause impairment of the motor functions. For examples if they occur on the joints such as the elbow or knee. When internal organs are stitched, the hyperfibrotic process may cause the formation of adhesions with the tissues surrounding the operation site.
Lastly, the use of ester derivatives of hyaluronic acid is known in the preparation of biomaterials, including suture threads, in the medical-surgical sector (European Patents EP 341745 and EP 216453).